Vacuum spark advance for ignition systems



y 1961 E. M. MASON 2,991,338

VACUUM SPARK ADVANCE FOR IGNITION SYSTEMS Filed Oct. 2, 1958 FIG. I EZfiSZQ a;

INVENTOR EDWARD M. MASON ATTORNEY United States Patent 2,991,338 7 MVACUUM SPARK ADVANCE FOR IGNITION SYSTEMS Edward M. Mason, St. Louis,Mo., assignor to ACF Industries, Incorporated, New York, N.Y., acorporation of New Jersey Filed Oct. 2, 1958, Ser. No. 764,901 7 Claims.(Cl. 200-31) This invention relates to vacuum-operated motors, and moreparticularly to a motor of this class which is especially useful as aspark advance mechanism for a distributor such as is used in theignition system for an internal combustion engine, though not limited tosuch use.

A conventional type of vacuum-operated spark advance mechanism comprisesa diaphragm-type motor, one side of the diaphragm of which is subject tovacuum derived from the intake manifold of the engine, the other side ofwhich is subject to atmospheric pressure. A return spring is provided inthe motor biasing the diaphragm toward an initial position of maximumretardation of the spark. The diaphragm is movable away from thisinitial position in spark-advancing direction upon increase of vacuum.

A present requirement of automotive engine designers is that thediaphragm be held in its initial position until the vacuum reaches apredetermined value, and that the diaphragm then moves through its fullstroke (fully to advance the spark) in response to a further increase invacuum which is considerably less than heretofore allowed. For example,it is now required that the diaphragm remain in its initial position upto a vacuum of 8 inches Hg, then move through its full travel onincrease of vacuum from 8 inches Hg to 12 inches Hg. Heretofore, it wasrequired that the diaphragm remain in its initial position up to avacuum of 7 to 8 inches Hg, but then a further increase in vacuum up to17 to 18 inches Hg was allowed to attain full travel of the diaphragm.

This prior requirement could be fulfilled simply by using a relativelystrong compression spring, strong enough to hold the diaphragm ininitial position until the vacuum reached 7 to 8 inches Hg, and thenbeing adapted to allow for full stroke of the diaphragm on increase ofvacuum up to 17 to 18 inches Hg. However, where the full stroke of thediaphragm has to be accomplished on increase of vacuum from 8 inches Hgto 12 inches Hg, for example, it is difficult if not impossible toprovide a spring which, while strong enough to hold the diaphragm ininitial position up to a vacuum of 8 inches Hg, is weak enough to allowfor full travel of the diaphragm on further increase of vacuum up toonly 12 inches Hg.

Accordingly, it is an object of this invention to provide a sparkadvance mechanism of the class described which, while being ofeconomical and compact construction, is capable of holding the diaphragm(or other equivalent movable element such as a piston) in its initialposition of maximum spark retardation up to a predetermined value ofvacuum, and then to allow for full stroke of the diaphragm on arelatively low further increase in vacuum.

In general, the object of the invention is attained by providing, inaddition to a return spring, a means which is operable only when thediaphragm (or other equivalent movable element) is in or near itsinitial position for exerting a supplemental hold on the diaphragm toretain it in its initial position, this means being rendered inoperativeto exert any substantial hold on the diaphragm upon movement of thediaphragm away from its initial position. More specifically, this meansis a magnetic means operable by magnetic attraction on the diaphragm.

Patented July 4, 1961 Other objects and features will be in partapparent and in part pointed out hereinafter.

The invention accordingly comprises the constructions hereinafterdescribed, the scope of the invention being indicated in the followingclaims.

In the accompanying drawings, in which one of various possibleembodiments of the invention is illustrated,

FIG. 1 is a plan view of a distributor provided with a spark advancemechanism of this invention, the cap of the distributor being removedand said mechanism being shown in section; and,

FIG. 2 is a vertical section on line 22 of FIG. 1, showing a portion ofthe cap.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

Referring to the drawings, there is indicated at 1 an ignitiondistributor for an internal combustion engine of the automotive type.This comprises the usual case 3 and cap 5. Only a part of the capappears in FIG. 2. A shaft 7 extends into the case through a bearing 9at the center of the bottom of the case. This shaft is driven by theengine. Shaft 7 drives the usual timer cam 11 through the usualspeed-responsive mechanism 13, the latter being adapted to change thephase of the cam relative to the shaft 7 in response to change in speedof the shaft. Cam 11 drives the usual rotor 15, part of which appears inFIG. 2, for contacting the usual distributor contacts (not shown) whichare carried by the cap. Cam 11 actuates the usual circuit breaker, whichis generally designated 17.

The circuit breaker 17 comprises a breaker plate 19 having a central hub21 rotatable in a bearing 23 centrally formed in a supporting plate 25fixed in the case 3. Adjustably mounted on the breaker plate 19 is aterminal 27 carrying a contact 29 adapted for engagement by a contact 31on a breaker arm 33 pivoted at 35 on plate 19. Arm 33 has a finger 37engageable with the cam 11 and is biased toward the cam by a spring 39.Terminal 27 is electrically connected by a wire 41 to a terminal 43.Terminal 27 is also electrically connected by a wire 45 to one terminalof condenser 47 mounted on the breaker plate 19. The other terminal ofthe condenser is elec trically connected to plate 19 by the metal caseof the condenser and a clip 49 which holds the condenser on plate 19,and plate 19 is grounded by means of a screw 51 threaded in plate 19, aclip 53 on the screw, and a wire 55 connected to the case 3.

The breaker plate 19 is rotatable in bearing 23 to change the phase offinger 37 relative to the cam 11 to advance or retard the spark, and adiaphragm-type motor 57 is provided for rotating the plate 19 for thispurpose. Motor 57 comprises a hollow body constituted by a cup-shapedhousing 59 and a cap 61 and containing a diaphragm 63. The diaphragm hasits margin clamped between the rim 65 of housing 59 and the rim 67 ofcap 61. As shown, clamping may be accomplished by swaging a portion 69of rim 65 over on rim 67. The base of the cup-shaped housing 59 isformed to have an outwardly extending cylindrical wall portion 71, aninwardly directed shoulder portion 73 at the outer end of the portion71, and a cylindrical extension 75 of smaller diameter than portion 71projecting outward from shoulder portion 73. Extension 75 is open at itsouter end. Housing 59 defines a chamber 77 on one side of diaphragm 63(its left side as illustrated in FIG. 1) which is open to the atmospherevia the openended extension 75. The base of the cup-shaped cap 61 isformed to have an outwardly extending cylindrical wall portion 79, aninwardly directed shoulder portion 81 at the outer end of portion 75,and a nipple 83 projecting outward from shoulder portion 81. Cap 61defines a vacuum chamber 85 on the other side of the diaphragm (itsright side as illustrated in FIG. 1) adapted for connection totheintake. manifold as by means of a line such as indicated at 87connected at one end to the nipple 83 and at its other end to the usualso called spark port of the carburetor for the engine.

The cylindrical extension 75 of the housing 59 is received in a bracket89 on the distributor case 3. A link 91 is secured at one end to thecenter of the diaphragm 63 and extends through the extension 75 and intothe case 3, having its. other end connected as by means of the screw 51to the breaker plate 19. The link is shown as having a longitudinal slot93 receiving a guide pin 95 extending across the extension 75, but thisis not essential. The link is secured to the diaphragm by having areduced end portion 97 which extends through a central hole in a cuppedwasher 99 on the one side of the diaphragm, a central hole in thediaphragm, a central hole in a cupped washer '101 on the other side ofthe diaphragm, and a central hole in flat washer 103 which backs up thewasher 101, the end of portion 97 being riveted over on washer E103.

Movement of the diaphragm 63 and the link 91 toward the left as viewedin FIG. 1 rotates the breaker plate 19 counterclockwise as viewed inFIG. 1 to retard the spark, and movement of the diaphragm and the linktoward the right rotates the plate clockwise to advance the spark.Movement of the diaphragm toward the right is against the resistance ofa coil compression spring 105 in cap 61 reacting from shoulder 81against washer 101. The end of the spring engaging washer '101 ismaintained centered by washer 103. The washers are all made ofmagnetizable metal, mild steel, for example, though only washer 99 needbe made of magnetic metal. A ring-shaped permanent magnet 107 is mountedin the housing 59 surrounding the link 91. As shown, the magnet isaccommodated in the recess defined by portions 71 and 73 of the base ofthe housing, being secured as by cement 109 to portion 73.

The arrangement is such that with atmospheric pressure in vacuum chamber85 (as when the engine is not running), spring 105 holds the diaphragm63 at the left end ofits stroke, determined by engagement of washer 99with magnet 107, in the position of maximum retardation of the spark.Magnet 107, by its attraction on the washer 99, adds a forcesupplementing the spring force to hold the diaphragm in the statedposition. When vacuum is established in vacuum chamber 85, diaphragm 63is subjected to differential of pressure on opposite sides (atmosphericpressure on its left side and lower pressure because of the vacuum onits right side), and the pressure differential acts in opposition to theforce of the spring 105 and the magnet 107. Upon increase of vacuum to avalue suificient to overcome the force of the spring and the magnet, thediaphragm moves toward the right, thereby drawing the 'washer 99 awayfrom the magnet. Upon separation of the washer 99 from the magnet,thereby establishing an air gap between the magnet and the washer, theforce exerted by the magnet drops oif sharply, and with furthermovementlof'the diaphragm to the right upon further slight increase invacuum, the magnet is substantially inefiective. Thereafter, uponfurther increase in vacuum, substantially 'the entire force resistingthe movement of the diaphragm toward the right is the force of thespring 105.

'With the above-described arrangement, it is readily possible to selecta spring 105 and a magnet 107 which will take care of a requirement forholding the diaphragm 63 in its'initial position of maximum retardation(its extreme left position as illustrated in FIG. '1) until the vacuumreaches a predetermined value (for example, 8 inches Hg), and forfull-stroke travel of the diaphragm upon a relatively low furtherincrease in 4 Hg). This is because the spring may be a relatively weakspring, since the spring need not be relied upon as the only source offorce for holding the diaphragm in its initial position, and with a weakspring it is possible to obtain full travel ofthe diaphragm on arelatively low increase in vacuum.

In view of the above, it will be seen that the several objects 'of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

I claim:

1. A vacuum-operated motor comprising means defining a vacuum chamber, amovable element closing said chamber subject on one side to vacuum inthe chamber, said element being adapted for movement in one directionupon increase of vacuum in said chamber, spring means biasing saidelement to move in the opposite direction toward an initial position andadapted to hold said element in said initial position with apredetermined force, and means operable only when said element is in orvnear its initial position for exerting a supplemental hold on saidelement to retain it in its initial position, said holding, means beingrendered inoperative to exert any substantial hold on said element uponmovement of said element away from its initial position.

2. A vacuum-operated motor comprising means defining a vacuum chamber, amovable element closing said chamber subject on one side to vacuum inthe chamber, said element being adapted for movement in one directionupon increase of vacuum in said chamber, spring means biasing saidelement to move in the opposite direction toward an initial position andadapted to hold said element in initial position with a predeterminedforce, and magnetic means operable by magnetic attraction only when saidelement is in or near its initial position for exerting a supplementalforce for holding said element in its initial position, said magneticmeans being rendered inoperative to exert any substantial force byattraction vacuum (for example, from 8 inches Hg' to 12 inches 15 uponmovement of said element away from its initial position. 7

3. A vacuum-operated motor comprising a body defining a vacuum chamber,a pressure-responsive diaphragm closing said chamber and subject on oneside to vacuum in the chamber and on the other side to atmosphericpressure, said diaphrgam having a magnetic member positioned thereon, apermanent magnet carried by the body on the atmospheric pressure side ofthe diaphragm, and spring means biasing the diaphragm in the directiontoward said magnet and to a limiting position determined by engagementof said magnetic member with said magnet.

4. A vacuum-operated spark advance mechanism for controlling an ignitiondistributor for an internal combustion engine by means of vacuum such asmay be derived from the intake manifold of the engine, said mechanismcomprising means defining a vacuum chamber, a movable element closingsaid chamber subject on one side to vacuum in the chamber, means forconnecting said element to the distributor, said element being adaptedfor movement in spark-advancing direction upon ncrease of vacuum in saidchamber, spring means biasmg sa d element to move in the oppositedirection toward an 1mtial position of maximum spark retardation andadapted to hold said element in said initial position with apredetermined force, and means operable only when said element is in ornear its initial position for exertmg a pp emental hold on said elementto retain it in its 1mal position, said holding means being renderedinoperative to exert any substantial hold on said element upon FQVQI IQM9f said element away from its initial position.

5. A vacuum-operated spark advance mechanism for controlling an ignitiondistributor for an internal combustion engine by means of vacuum such asmay be derived from the intake manifold of the engine, said mechanismcomprising a body defining a vacuum chamber adapted for connection tothe intake manifold, a movable pressure-responsive element carried bythe body closing said chamber and subject on one side to vacuum in thechamber and on the other side to atmospheric pressure, means forconnecting said element to the distributor, said element being adaptedfor movement in spark-advancing direction by atmospheric pressure uponincrease of vacuum in said chamber, spring means biasing said element tomove in the opposite direction toward an initial position of maximumspark retardation and adapted to hold said element in initial positionwith a predetermined force, said element being at least in partmagnetic, and a permanent magnet carried by the body for attracting saidelement to its said initial position, said magnet being ineffective toexert any substantial force by attraction upon movement of said elementaway from its initial position.

6. A vacuum-operated spark advance mechanism for controlling an ignitiondistributor for an internal combustion engine by means of vacuum such asmay be derived from the intake manifold of the engine, said mechanismcomprising a body defining a vacuum chamber adapted for connection tothe intake manifold, a pressure-responsive diaphragm carried by the bodyclosing said chamber and subject on one side to vacuum in the chamberand on the other side to atmospheric pressure, said diaphragm having amagnetic member positioned thereon, means for connecting said diaphragmto the distributor, a permanent magnet carried by the body on theatmospheric pressure side of said diaphragm, said diaphragm beingadapted for movement in spark-advancing direction away from the magnetby atmospheric pressure upon increase of vacuum in said chamber, andspring means biasing said diaphragm in the opposite direction toward aninitial position of maximum spark retardation determined by engagementof said magnetic member with said magnet.

7. A vacuum-operated spark advance mechanism for controlling an ignitiondistributor for an internal com bustion engine by means of vacuum suchas may be derived from the intake manifold of the engine, said mechanismcomprising a body defining a vacuum chamber adapted for connection tothe intake manifold, a movable pressure-responsive diaphragm attached atits margin to the body closing said chamber and subject on one side tovacuum in the chamber and on the other side to atmospheric pressure, alink for connecting said diaphragm to the distributor, said link beingconnected to the diaphragm by means including a magnetic Washer on theatmospheric pressure side of the diaphragm, a permanent magnet carriedby the body on the atmospheric pressure side of said element, saiddiaphragm being adapted for movement in spark-advancing direction awayfrom the magnet by atmospheric pressure upon increase of vacuum in saidchamber, and a compression spring in said chamber biasing said diaphragmin the opposite direction toward an initial position of maximum sparkretardation determined by engagement of said washer with said magnet,said magnet being ring-shape, and said link extending through saidmagnet.

References Cited in the file of this patent UNITED STATES PATENTS2,302,685 Dyer Nov. 24, 1942 2,628,296 Dillman Feb. 10, 1953 2,640,116Dyer et al May 26, 1953 2,643,304 Lautzenhiser June 23, 1953 2,717,286Bales Sept. 6, 1955 2,922,002 Gilman Jan. 19, 1960

